There are plenty of young contenders vying for his place as leading man, but very few can come close to veteran actor Robert Redford.

In fact it is difficult to believe the star has a career spanning four decades. His first film was released back in 1961 - the instantly forgettable War Hunt - but since then he has become one of America's all-time great box office successes and his chiselled jawline has made him a heart-throb the world over.

Today, Redford is still top of the game and at the age of 65, more in demand than ever. He recently starred alongside Brad Pitt in the movie Spy Game and hot on the heels of that comes his new prison thriller The Last Castle.

Both roles see Redford dominating the big screen and running rings around his younger co-stars. And that probably has a lot to do with his laid-back attitude towards ageing.

"The only time I think about it is when it is put in front of me," he shrugs. "I noticed about 10 years ago people would say, `I notice you're more wrinkled'. But I just thought, `Yeah that's what happens.' Besides a person's road map is there to be seen and shared," he adds philosophically.

It is hardly surprising that Redford is still way ahead in his field. He has never relied on his looks - despite being one of Hollywood's biggest sex symbols - and has often chosen heavyweight political scripts over surefire commercial hits.

"A lot of the films I like to make are about what happens to the individual when the system that is supposed to be protecting you is actually robbing you," he explains.

That's mostly why he was drawn to The Last Castle. In the film, which opens this week, Redford plays a brilliant general, who is court-marshalled and stripped of his rank. He is sent to a military prison where he becomes embroiled in a battle of wills with the sadistic governor.

"It boils down to a simple right or wrong situation," explains Redford. "The man controlling the prison believes he has to control the violence and threat of any kind of uprising with dehumanising tactics. He constantly brings out the worst in them.

"My character, being the kind of leader he was, knows the importance of galvanising the men to a kind of sweeter core - extracting the best of them."

During shooting Redford had first-hand experience of what life would really have been like for his character as most of the scenes were shot in an actual state penitentiary.

"You were around death row all the time," he says. "We were in tiers of tiny cells but in reality they'd have three in a cell in an effort to dehumanise people."

Redford's obvious passion for justice and the cause of the underdog is just as fervent off screen too. He is a huge environmentalist and eschews the Hollywood lifestyle for a rural existence in Utah.

"I bought two acres of land there for 500 dollars in 1961. I bought it because when I saw it I thought this is the most exquisite piece of land I've seen in a long time. I love to fly-fish. I work with horses. I have horses of my own. I live in the mountains, in a semi-wilderness area, very close to nature," he smiles.

"I don't see myself exclusively country, but my heart is in nature. There's no question I don't fall easily into line with what goes on in Hollywood and the way it goes on and I don't have a lot of use for the business of the business," he states.

"I always say to younger actors, have another life because it's a tough business. It's a cruel, often brutal business to your psyche."

Despite his high profile, Redford has always managed to keep his own private life intensely private. He has never discussed the break up of his 27-year marriage to Lola Van Wagenen or his subsequent romances. The father of three and grandfather of four is, however, a lot more vocal when it comes to the other big love of his life - The Sundance Institute which he founded 20 years ago. The Institute spawned the Sundance Film Festival which has since gone from strength to strength.

He says: "It turned out to be something far more personal than I ever imagined. So much so when you're that passionate about something you get so far into it, I got a little lost for a while."

He is referring to his 1998 romance The Horse Whisperer, which he directed and starred in and which didn't exactly gallop ahead at the box office. Then there was last year's expensive flop The Legend of Bagger Vance, which he also directed. But as well as being older Redford is certainly wiser and quickly realised the key to getting back on track was returning to the thing he loves most - acting.

"I missed just acting," he says with a warm smile. "That is how I started out and although I've had mixed feelings about it in the past it's still the first love."